The present invention relates generally to numerical control driving systems, and more particularly to those systems that specify control values for discrete calibration intervals.
In many technical applications of driving systems, as used for example in conveying machinery, elevators, machine tools, industrial robots, rolling-mill installations or vehicle control systems, it is necessary to generate a sequence of movements in accordance with defined paths. In numerically controlled driving systems, a sequence of position settings is preselected in one or more coordinates over a specific time cycle. The control system must calculate a precise acceleration and velocity profile for the transition between two position settings and transmit this profile to the driving system. The goal is to use the permissible traversing velocities and the available driving power as efficiently as possible without distorting the contour through limiting effects or overshooting.
Because numerical control system preselect cycle time, any change in, or stipulation of acceleration settings or velocity settings can only occur at discrete times. Therefore, inaccuracies within the range of one clock interval must be avoided.
DE-PS 26 43 148 describes a method of numerically controlling an element of a machine tool along a specified path of motion, whereby in each calibration interval, the discrete acceleration values, the discrete velocity values and the path increments to be travelled are calculated by a computer. A braking command dependent on acceleration, velocity and residual path is then generated by a processor for a complete calibration interval during which the brake is applied. The braking command is then interrupted for at least one calibration interval, provided that the ideal braking parabola is not exceeded. With this method, however, it is not possible to reach a specified target point exactly at the beginning of a calibration interval.
The goal of the present invention is to develop numerical positioning control systems in a way which will allow drive values to be specified at a calibration time and a desired target point to be reached with a desired final velocity exactly at the beginning of a calibration interval.